One common disk drive design generally includes at least one data storage disk (e.g., magnetic) with concentric data tracks, an air bearing slider for each data storage surface of each data storage disk that includes a read/write head for reading and writing data on the various data tracks on the corresponding data storage surface, an actuator arm assembly (generally including a rigid actuator arm or tip and a suspension) for holding the slider over the corresponding data storage surface, and a voice coil motor for moving the actuator arm assembly, and hence the head(s), across the corresponding data storage surface to the desired data track and holding the head over the relevant data track during a read or write operation. The air bearing slider flies above its corresponding data storage surface during disk drive operations on a boundary layer of air that is carried by the rotating data storage disk and that is appropriately compressed by the slider.
Disk drives increasingly reflect a need to improve the density at which information can be recorded on and reliably read from a data storage medium, e.g. a disk. Because the recording density of a disk drive is effectively limited by the distance between the head and the data storage medium, a goal of most flying-type slider designs is to operate a slider as closely as possible to a data storage medium while avoiding physical impact with the medium. In slider air bearing designs, a minimal amount of clearance (fly height) of the slider relative to the data storage medium is preferred so that the head can distinguish magnetic fields emanating from adjacently spaced tracks on the data storage medium.
Disk drive operations ideally require the slider to maintain a constant spacing between the read/write head and the data storage medium across all of the data tracks, from the central portion to the outer periphery of the data storage medium, e.g. a disk. This requirement presents a key technical challenge since the air velocity created by a rotating disk varies in both magnitude and direction relative to the annular position of the slider about the data storage medium. The problem is further exacerbated for disk drives having rotary actuators since slider pitch generally varies with respect to the annular position of the slider about the data storage medium. Thus, in addition to achieving an optimal minimal average spacing between the data storage medium and the slider, it is critical that the slider fly at a relatively constant height notwithstanding the variation in conditions the slider experiences during normal operation of the disk drive.
A slider may experience fly height disparities due to variations in one or both pitch and lateral roll. “Pitch” is a measure of the angle formed between the longitudinal axis of the slider and the direction of rotation of the data storage medium as measured in a plane parallel to a major surface of the data storage medium. The pitch of the slider varies in a disk drive as the slider moves from track to track across the data storage medium. The pitch of the slider also varies in a disk drive when the slider moves in response to forces, e.g. stress, exerted upon it. Lateral roll, on the other hand, is a measure of the angle of rotation about the longitudinal axis of the slider. Variations in lateral roll occur when a slider experiences a skewed air flow and/or when the slider impacts the data storage medium e.g. during a contact event or loading/unloading of the slider relative to the corresponding data storage medium.
A slider also experiences varying conditions during movement of the positioning system as it accesses data on various portions of the data storage medium. Movement of the slider across the data storage medium can lead to dramatic variation in lateral roll and pitch, and a resultant variation in fly height which could result in the slider contacting the surface of the data storage medium. The above-noted phenomena are all reasons that a slider must be able to manage pitch and roll variations. Additionally, contact events such as dropping or striking the disk drive can cause the slider to contact and damage the data storage medium.
A wide variety of disk drive and slider designs have been proposed and implemented to reduce damage to the data storage medium and/or reduce the frequency of contact between the slider and the data storage medium. Specifically, harder disk substrates have been employed to reduce damage inflicted upon the disk due to contact from the slider. However, such a development simply requires even greater control of the pitch and lateral roll of the slider since contact with the harder disk can potentially damage the slider. Additionally, blends have been added to the corners of one or more air bearing surfaces of conventional sliders, but this has resulted in sliders which demonstrate wide variations in one or more of fly height, pitch, and lateral roll. Finally, pads have been proposed for the lower surface of the slider for providing a contact surface during a shock event and in load/unload operations. Notwithstanding these efforts, it would be desirable to develop a slider design which prevents damage to the disk surface during any of contact, loading, and operation.